1. Field of the Invention
The present invention relates to resin compositions which have good curing capability and storage stability. The invention further relates to cured products prepared by curing such a composition. The present invention also relates to novel ionic liquids which are useful as curing accelerators and/or curing agents.
2. Discussion of the Background
An epoxy resin composition is a general-purpose synthetic resin widely utilized in various fields of adhesives, sealants, coating agents, etc. A “two-component” epoxy resin composition was once the mainstream, but because of its troublesome and inconvenience in that the main ingredient and the curing agent must be mixed just before use, a “one-component” epoxy resin composition has been developed.
JP-A 06-211969 discloses a most typical “one-component” epoxy resin composition that comprises a dicyandiamide, a dihydrazide compound or an amine adduct compound as a “solid dispersion-type curing accelerator”. These have a special structure, and could not always be said to be easily available.
On the other hand, Polimery, vol. 48, pp. 833-835 (2003) reports that a specific ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate is usable as a curing agent for epoxy resin. However, the curing temperature is at least 190° C. and is high, and even when it is added in an amount of from 1 to 5 parts by weight relative to 100 parts by weight of epoxy resin, it needs a long period of time of from 6.5 to 7 hours; and therefore, it is not on a practicable level at all.
Thus, conventional curing agents and curing accelerators for use in epoxy resin compositions have various problems as described above, and could not always be said as practicable resin compositions of excellent operability and reliability.